University of Torino Dip. Chimica IFM. 6-11/09/2009 Torino

Transcription

1 Transton State Search wth CRYSTAL09 Albert Rmola nversty of Torno Dp. Chmca IFM 6-/09/009 Torno

2 Chemcal Reactvty n Quantum Chemstry Why to localze Transton States (TS) TEORETICALLY? Relevance n CEMICAL REACTIVITY TS E Reactant (R) E r Product (P)

3 L L gradent vector = = g g g g ) ( ) ( K K K r statonary ponts 0 ) ( = g K r Chemcal Chemcal Reactvty Reactvty n Quantum n Quantum Chemstry Chemstry essan matrx = = L M O M M L L M O M M L 3N-6 0 = = D P P λ λ λ L M O M M L L dagonalzable egenvalues 3

4 Chemcal Reactvty n Quantum Chemstry nd order Saddle Pont 3N-8 egenvalues > 0 + egenvalues < 0 E R P st st order Saddle Pont or TS 3N-7 egenvalues > 0 + egenvalue < 0 P R mnma 3N-6 egenvalues > 0 4

5 Chemcal Reactvty n Quantum Chemstry ow to fnd TS theoretcally? mnmze n 3N-7 drectons maxmze n drecton P R Perodc plane-wave codes (VASP QuantumEspresso CPMD) Quantum Molecular codes (Gaussan NWChem CRYSTAL) Nudged Elastc Band NEB Dstngushed Reacton Coordnate DRC 5

6 Nudged Elastc Band (NEB) Lnear nterpolaton between reactants and products Obtanng the mnmum energy path (MEP) Images MEP R P R P

7 Dstngushed Reacton Coordnate (DRC) Based on a scan along one nternal coordnate ( ) of the system R P R P SCAN SCAN 7

8 DRC: Strategy to Follow Two successve steps: Step. Defnng a geometry close to a TS Va scan calculaton of an nternal coordnate that drves the reacton from R to P Step. Geometry optmzaton of a TS Refnng the structure found n Step through the approprate algorthm Step Step R P 8

9 DRC Step : Scan Calculaton Example : keto-enol tautomerzaton of C(-O)N C(=O)N O E r O C N Reactant -53 kj mol - C N Product Choose of the nternal coordnate for the scan calculaton SCAN -N [.3 -.0] Å 4 steps of -0. Å 9

10 DRC Step : Scan Calculaton E number of steps (-N dstance) 0

11 DRC Step : Scan Calculaton Example : proton jump n 3D -edngtonte S O O Al E r S O Al O Reactant -5 kj mol - Product Choose of the nternal coordnate for the scan calculaton O O SCAN -O [.8.] Å 8 steps of -0. Å

12 DRC Step : Scan Calculaton E dstngushed energy profle O (Å)

13 DRC Step : TS geometry optmzaton Intal guess Optmzed TS Energy profle TS 39 R 0 P R 0 TS 33 P

14 Input CRYSTAL09. Scan Calculaton geometry nput block OPTGEOM FLLOPTG BFGS ALLOWTRSTR Keyword of optmzaton Optmzaton atomc coord. + cell param. Opt. va BFGS update scheme pdate of the trust radus at each opt. step INTREDN Optmzaton n nternal coordnates LNGSFROZEN (ANGSFROZEN or FREEZDI) Keyword to freeze nternal coordnates Number of bond lengths (ang. or dh.) to freeze Label at. Label at. Cell ndex at. SCANRED Keyword to perform a scan calculaton.0 5 Bond length () angle () dhedral (3) Fnal value nternal coordnate Number of steps FINALRN 4 Acton after geometry optmzaton [Sngle pont + gradent] n 4

15 Input CRYSTAL09. TS Calculaton geometry nput block OPTGEOM FLLOPTG Keyword for optmzaton Optmzaton atomc coord. + cell param. BFGS TSOPT Opt. of a transton state geometry ESSNM TRSTRADIS Numercal estmate of the ntal essan matrx Defnes an ntal value for trust radus 0. MAXTRADIS Defnes a maxmum value for trust radus 0. amltonan SCF&C nput block TOLDEE Energy tolerance between SCF cycles 5

16 Fnal Example: Proton Jump n -CA B3LYP O Al S : 3G* O: 6-3G* I S: 66-G* Al: 88-3G* II SCAN OII (for both cases!) 6

17 Fnal Example: Proton Jump n -CA Wthout O Wth O cm cm -

18 Fnal Example: Proton Jump n -CA Absence of O E el Presence of O 5 [ G 98 ] [] 0 [0] [] kcal mol [4] 3 [0] [3] 8

19 Robustness of the DRC Method Proton jump I II Serka and Sauer J. Phys. Chem. B (00) 05:603 CRYSTAL full B3LYP : 3G* O: 6-3G* S: 66-G* Al: 88-3G* CRYSTAL full B3LYP : 3G* O: 6-3G* S: 88-3G* Al: 88-3G* QM-Pot B3LYP (nner regon) S Al: Ahlrch s DZP O: Ahlrch s TZP E 5.0 kcal mol - E 7. kcal mol - E 7.6 kcal mol -

20 Transton State Search wth CRYSTAL09 Albert Rmola nversty of Torno Dp. Chmca IFM 6-/09/009 Torno